How to create a fan curve?

Samoht · August 22, 2014

Hey guys,

I'm pretty new to building my own PC, overclocking and all that good stuff. I was reading quite a lot the past few days and one thing that allways comes up when it comes to keeping components as cool and quiet as possible are custom fan curves. Now I do know that I can set them up depndend on various tempertures in my PC using SpeedFan. I also know that it should be an exponential curve, but I don't understand how I would determine which exact form the curve needs to have.

From my thinking I would be stress testing the part I want to create the fan curve for and plot its temperture in a graph and the somehow translate this graph into a fan curve. But the first problem that comes in my head is, that the momentary fan curve would clearly influence that measurement. The second problem is that I would have no exact idea how i would turn this data into a fan control graph. Sure at first I would determine at which percentage my fan can run while remaining silent to create something like a starting point, but what comes next? Ho do I proceed from that?

Would be great if someone takes the time to actually read all that and could explain all that to me.

With best regards Thomas.

PS. Please excuse my questionable english skills.

Majestic · August 22, 2014

Most motherboards just use a ramp function. You set 4 parameters (min. fanspeed, max. fanspeed + min cpu temp, max cpu temp) and creates the graph for you.

However, what fanspeeds these need to be depends on what is required. Most of the times, fanspeeds of casefans have a high diminishing return. So you can leave those at whichever level is comfortable to you.

for CPU fans, it depends on the type. Min. fanspeed is just the lowest the fan can handle, and the max fanspeed is just determined by finding the required fanspeed needed to keep the component cool. So, for an intel chip this means under ~72deg (yes i know cores can go higher).

For the GPU, you need to do the same, only with afterburner instead of BIOS.

LogicalDrm · August 23, 2014

This is actually simpler than you think. First pick the maximum fan speed (in %) you want them to run. Then you pick the maximum temp that speed needs to cool. For me that point is 80% at 60C. Then you pick the low point using same method. For most fans minimum speed is 20-30%. So you set that with lowest temp CPU has, which is probably 30-40C. You can pick middle points too, but they aren't really necessary.

Now just add points along the way. My line is straight. For GPU is more exponential but I use less points on that anyway. Exponential means that it will raise quicker towards end.